N‐Heterocyclic Carbene Stabilized Dicarbondiphosphides: Strong Neutral Four‐Membered Heterocyclic 6π‐Electron Donors

Abstract

In contrast to cyclic π‐conjugated hydrocarbons, the coordination chemistry of inorganic heterocycles is less developed. Dicarbondiphosphides stabilized by N‐heterocyclic carbenes (NHCs) NHC→C2P2←NHC (1 a,b) (NHC=IPr or SIPr) contain a four‐membered C2P2 ring with an aromatic 6π‐electron configuration. These heterocycles coordinate to a variety of complex fragments with metals from groups 6, 9, and 10, namely [M0(CO)3] (M=Cr, Mo), [CoI(CO)2]+, or [NiIIBr2], through an η4‐coordination mode, leading to complexes 2 a,b, 3 a,b, 5 a,b, and 6 a,b, respectively. These complexes were characterized by X‐ray diffraction methods using single crystals, IR spectroscopy, and DFT calculations. In combination these methods indicate that 1 a,b behave as exceptionally strong 6π‐electron donors.

Insertion of Ruthenium into an inorganic, cyclic biradicaloid

“…The non‐Kekulé molecule B with a central P 2 N 2 heterocycle, which is best described as a biradicaloid, has been intensively investigated in the last decade [8–9] . The addition to small molecules„ [9–10] radical reactivity, [11] complexation of metal fragments, [12–14] and ring expansion by insertion of an organic moiety has been reported [15] . In the reaction with carbon monoxide or isonitriles, the expansion of the four‐membered to a five‐membered ring such as C is achieved by insertion of the carbon atom (Scheme 1).…”

Bis(imidazolium)‐1,3‐diphosphete‐diide: A Building Block for FeC2P2 Complexes and Clusters

“…Heterocycle 1 is easily oxidized at E°= À 0.451 V (vs. Fc/Fc + ) to its persistent radical cation [23] and binds to M(CO) 3 fragments (M = Cr, Mo) as electron donating ligand. [24] Here, we report that 1 not only allows to prepare neutral iron dicarbonyl complexes, which-in contrast to arene complexes-are remarkably stable but also show a rich redox chemistry. Specifically, a comparison between [Fe-(CO) 3 -η 4 -{(IPr) 2 C 2 P 2 }] 2 + and [Fe(CO) 2 -η 4 -{(IPr) 2 C 2 P 2 }] will show that subtle differences in the structure may lead to significant differences in the electronic structure of the central FeC 2 P 2 core.…”

Bis(imidazolium)‐1,3‐diphosphete‐diide: A Building Block for FeC2P2 Complexes and Clusters

“…Both descriptions lead to a central aromatic 6π‐electron system delocalized over the C 2 P 2 ring. Heterocycle 1 is easily oxidized at E °=−0.451 V (vs. Fc/Fc + ) to its persistent radical cation [23] and binds to M(CO) 3 fragments (M=Cr, Mo) as electron donating ligand [24] …”

“…Heterocycle 1 is easily oxidized at E °=−0.451 V (vs. Fc/Fc + ) to its persistent radical cation [23] and binds to M(CO) 3 fragments (M=Cr, Mo) as electron donating ligand. [24] …”